# 3.15. One Installation, Multiple Instances

This is a somewhat specialist feature; if you don’t know whether you need it, you don’t. It is useful to admins who want to run many separate instances of Bugzilla from a single installed codebase.

This is possible by using the `PROJECT` environment variable. When accessed, Bugzilla checks for the existence of this variable, and if present, uses its value to check for an alternative configuration file named `localconfig.<PROJECT>` in the same location as the default one (`localconfig`). It also checks for customized templates in a directory named `<PROJECT>` in the same location as the default one (`template/<langcode>`). By default this is `template/en/default` so `PROJECT`’s templates would be located at `template/en/PROJECT`.

To set up an alternate installation, just export `PROJECT=foo` before running checksetup.pl for the first time. It will result in a file called `localconfig.foo` instead of `localconfig`. Edit this file as described above, with reference to a new database, and re-run checksetup.pl to populate it. That’s all.

Now you have to configure the web server to pass this environment variable when accessed via an alternate URL, such as virtual host for instance. The following is an example of how you could do it in Apache, other Webservers may differ.

    <VirtualHost 12.34.56.78:80>
        ServerName bugzilla.example.com
        SetEnv PROJECT foo
    </VirtualHost>

Don’t forget to also export this variable before accessing Bugzilla by other means, such as repeating tasks like those above.

This documentation undoubtedly has bugs; if you find some, please file them here.